EP0052022A1 - Dispositif pour calibrer un détecteur magnétique d'azimut dans un avion et méthode utilisant un détecteur de test - Google Patents

Dispositif pour calibrer un détecteur magnétique d'azimut dans un avion et méthode utilisant un détecteur de test Download PDF

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Publication number
EP0052022A1
EP0052022A1 EP81401420A EP81401420A EP0052022A1 EP 0052022 A1 EP0052022 A1 EP 0052022A1 EP 81401420 A EP81401420 A EP 81401420A EP 81401420 A EP81401420 A EP 81401420A EP 0052022 A1 EP0052022 A1 EP 0052022A1
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EP
European Patent Office
Prior art keywords
detector
service
test
magnetic field
craft
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Granted
Application number
EP81401420A
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German (de)
English (en)
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EP0052022B1 (fr
Inventor
Bernard P. Gollomp
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Bendix Corp
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Bendix Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C17/00—Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes
    • G01C17/38—Testing, calibrating, or compensating of compasses

Definitions

  • the present invention relates to a calibrator for calibrating a service magnetic azimuth detector of a craft and a method employing a test magnetic azimuth detector for calibrating said service detector.
  • Known compass calibrators inject two precision currents into a magnetic azimuth detector (also referred to as a flux gate or a:flux valve) to simulate rotation of the magnetic field of the earth while the aircraft is physically aligned to magnetic north.
  • a magnetic azimuth detector also referred to as a flux gate or a:flux valve
  • the magnitudes of these currents are determined when the magnetic azimuth detector is outside and away from the magnetic disturbances of the aircraft.
  • the magnetic azimuth detector is aligned to magnetic north and optical alignment equipment (e.g. telescope with reticle) is mounted to the magnetic azimuth detector and aimed at a distant monument, structure or geographic feature. Thereafter the magnetic azimuth detector is mounted in the craft using optical realignment equipment and precision currents are injected to simulate rotation.
  • optical alignment equipment e.g. telescope with reticle
  • the magnetic azimuth detector is corrected by a directional gyro or stable inertial platform. While this approach provides reasonably good accuracy, the initial heading of the aircraft must be precisely known.
  • the present invention overcomes the limitations and disadvantages of the prior art arrangements by providing a calibrator for calibrating a service magnetic azimuth detector of a craft, said service detector being responsive to the magnetic field of the earth to provide a service heading signal, said calibrator comprising: a test magnetic azimuth detector for providing a test heading signal signifying the magnetic orientation of said test detector with respect to the prevailing magnetic field of the earth; turntable means adapted to rotatably support said service detector; and calibration means connected to said test detector and responsive to said test heading signal, said calibration means being operable to determine the variation in said test heading signal due to changes in the magnetic field of the earth, and said calibration means being operable to connect to said service detector and determine the difference in said service heading signal when said craft is adjacent to and removed from said service detector.
  • a method employing a test magnetic azimuth detector for calibrating a service magnetic azimuth detector of a craft, each of said detectors being responsive to the magnetic field of the earth to provide a heading signal, said method comprising the steps of: subjecting said service detector to a rotating magnetic field while said craft is absent and while said craft is present; monitoring changes in the magnetic field of the earth with said test detector; measuring a change in the heading signal from when said craft is absent to when it is present for said service detector; and resolving said change in the heading signal of said service detector into at least one spatial harmonic component.
  • a test magnetic azimuth detector is operated in an open field to determine its characteristics and the changes in the prevailing magnetic field on the earth.
  • the magnetic characteristics of the open field need not exhibit a specific regularity but need only be stable.
  • This service magnetic azimuth detector is removed from its aircraft and is tested by either physical rotation or by application of a simulated rotating magnetic field to determine its characteristics in an open field.
  • the test detector will also be subjected to this rotational test. Since the characteristics of the test detector were previously measured under laboratory conditions and its errors determined, the direction of the earth's magnetic field in the open field can be accurately measured by the test detector.
  • This direction is established with respect to a reference monument or a line that may be laid on the ground in a northerly or any other arbitrary but fixed direction.
  • the service detector is installed in its craft and the test detector is mounted adjacent thereto. Once mounted in this manner both the service detector and, if desired, the test detector are then subjected to a rotating magnetic field to determine their characteristics in the presence of the craft. While this rotating magnetic field could be obtained by physically rotating each detector, preferably, it is obtained by injecting precision currents into each detector to simulate an externally rotating magnetic field.
  • the differential change in the response of a service detector due to the presence of the craft is subjected to Fourier analysis.
  • This analysis resolves the differential data into the one and two cycle errors caused by the presence of the aircraft.
  • the service detector is biased by injecting into it currents which produce an internal, biasing, magnetic field.
  • the injected currents are adjusted until the performance of the service detector approximately matches that previously measured in the open field.
  • the injection currents producing this convergence are then trigonometrically resolved to determine the azimuthal change in the prevailing magnetic field prevailing in the presence of the aircraft.
  • the service detector is readjusted to align it along the craft centerline. This latter alignment is achievable since previously recorded were the angular orientation of the aircraft along a reference line and the magnetic field prevailing in the presence of the aircraft with respect to that reference line, in a manner described hereinafter.
  • the service detector is biased by magnets or by injecting biasing signals until the service detector reads the actual heading with respect to the magnetic field prevailing in the open field.
  • This actual heading is known since the prevailing magnetic field was measured in the open field with respect to a reference line and the craft angular orientation with respect to that reference line was also known. This adjustment corrects for one cycle errors.
  • the service detector can also be compensated for two cycle errors in a conventional manner.
  • the foregoing adjusments are accomplished through apparatus employing programmable resistor networks driven by precision power supplies.
  • the networks provide precision currents, which may be switched through switches to either the service or test detector to determine their characteristics.
  • test magnetic detector 10 or test detector is a magnetic azimuth detector of conventional construction employing three, equiangular, electromagnetic arms (not shown) which, depending upon its azimuthal position, conducts a varying amount of the earth's magnetic field through its arms.
  • the magnetic intensity in each arm affects the harmonic content of alternating magnetic fields impressed therein by an associated driving coil.
  • Test detector 10 can be oriented into any desired azimuthal position.
  • the heading signal produced by test detector 10 is connected to coupler 14.
  • coupler 14 is a plurality of switches 14 cooperating with its associated group of switches 16, in a manner described hereinafter.
  • Switches 14 and 16 can employ a plurality of known devices such as relays.
  • a service detector is shown herein as aircraft magnetic azimuth detector 18 or service detector. This service detector is shown connected by a pair of data lines to switches 14. In this embodiment, service detector 18 is constructed similarly to detector 10. Both detectors 10 and 18 have windings on their respective branch arms which can be biased to produce a rotatable, magnetic field. Currents can be injected into these windings through switches 14. Service detector 18 is rotatably mounted on a turntable means, shown herein as index mount or turntable 12. In this embodiment, turntable 12 employs a transducer that produces a signal indicating the angular displacement of the turntable 12 and its associated service detector 18. This transducer signal is coupled to switches 14. Known angular transducers are used for this purpose.
  • the heading signals produced by detectors 10 and 18 may be analyzed by coupling one of them through switches 14 to analog signal conditioning device 20.
  • This device can use any one of various conventional techniques to obtain an angular measurement.
  • operational amplifiers can be used effectively to reproduce the well-known "Scott connection", thereby providing sine and cosine outputs on lines 20A and 20B, respectively.
  • Switches 16 are connected to lines 20A and 20B and can substitute for them lines 22 and 24. Lines 22 and 24 provide precision currents from precision controlled current sources, as power supplies 28 and 26, respectively. Accordingly, switches 16 can substitute precise signals for those provided from the analog signal conditioning device 20 and thereby perform a self-calibrating function. Specifically, the calibrated current injected through switches 16 is verified as producing a predetermined response.
  • Detector 30 is a synchronous detector for changing a harmonic (nominally 800 Hertz) into a direct current signal, which is then applied to analog to digital converter 32.
  • a calibration means employing a memory means is formed of a processor and memory or a microcomputer 34.
  • Microcomputer 34 responds to the output lines connected to it from converter 32 and the controls, block 36, as shown.
  • Microcomputer 34 also generates appropriate display signals which are displayed as indicated by the display part of block 36.
  • Microcomputer 34 provides control signals on its various output lines to switches 14 and 16, precision power supplies 26 and 28, detector 30, converter 32, and other devices described hereinafter.
  • the various data output lines of microcomputer 34 are shown broken to distinguish them from the other signal processing lines and enhance clarity.
  • Microcomputer 34 can operate the various switches 14 and 16 and can also provide a control signal to detector 30 to regulate its operational parameters such as its bandwith or demodulation rate.
  • converter 32 can be synchronized and interrogated by microcomputer 34.
  • the outputsof precision power supplies 26 and 28 can be adjusted in discrete steps by signals applied thereto from microcomputer 34.
  • Lines 38 and 40 of precision power supplies 26 are and 28/connected to programmable resistor networks 42 and 44, respectively.
  • Networks 42 and 44 are conventional resistor ladder networks whose internal switches operate to provide a variable current to switches 14.
  • the control over the variable current provided by networks 42 and 44 is by output lines of microcomputer 34.
  • supply 26 / and network 42 as well as supply 28 and network 44 operate as a controlled current source for applying a variable current to detectors 10 and 18 to energize their internal coils and simulate rotation of the magnetic field of the earth.
  • Power supply 46 shown controlled by an output line of microcomputer 34, is connected to switches 14 to inject a 400 Hertz reference signal to either detector 10 or 18 to operate its magnetic circuit in a well-understood manner.
  • Microcomputer 34 has stored in memory the characteristics of test detector 10 originally obtained by testing it in a Helmholz coil. These memorized characteristics signify the expected output from test detector 10 for various orientations. Microcomputer 34 operates switches 14, activates supplies 26 and 28 and adjusts networks 42 and 44 so that they couple through switches 14 a varying pair of biasing currents to the coils of test detector 10. These currents are sized to simulate rotation of the earth's magnetic field with respect to test detector 10. Test detector 10 consequently couples, through switches 14, to conditioning device 20 heading information in the form of harmonic components buried in the 400 Hertz carrier frequency.
  • conditioning device 20 simulates a "Scott connection" to produce signals signifying the sine and cosine of heading. These heading signals are filtered and synchronously detected by detector 30 to provide a direct current signal whose magnitude is proportional to heading. This signal is converted into digital form by converter 32 and applied to microcomputer 34. The pattern of this data is compared by microcomputer 34 to the stored pattern previously obtained under laboratory conditions to determine that the test detector 10 is still operating in its usual manner. Also, since the errors of the test detector 10 are known in advance, the operator can accurately determine the direction of the magnetic field of the earth in the open field. This may be done by rotating test detector 10 until it produces a predetermined output heading signal signifying alignment with the prevailing magnetic field of the earth.
  • service detector 18 is removed from its aircraft.
  • Service detector 18 is then connected by switches 14, under the control of microcomputer 34, to signal conditioning device 20.
  • Microcomputer 34 now stimulates and records the outputs of service detector 18 by electrically subjecting it to a rotating magnetic field caused by injection of biasing currents from networks 42 and 44 through switches 14. It is to be appreciated that in some embodiments instead of rotating the magnetic field electrically, the index mount 12 and thus service detector 18 may be mechanically rotated to achieve the same result.
  • this reference line is shown as north line N, a fiduciary line painted on an apron at an airport. While in this embodiment reference line N is aligned to magnetic north, such alignment is unnecessary provided the reference line is fixed.
  • the deviation of aircraft 50 (FIGURE 2) from reference line N, angle a is measured by suspending a plumb line from the center line of the craft and measuring the displacement of the center line from the reference line N at two positions. The angular measurement so obtained is entered into microcomputer memory, through controls,block 36, (Fig. 1).
  • Magnetic vectors Be represents the magnitude and the direction of that magnetic field prevailing in the absence of aircraft 50.
  • FIGURE 2 the presence of aircraft 50 changes the magnitude and direction of the prevailing magnetic field, this disturbed field being illustrated as vector Bp.
  • the net change in magnetic field is indicated by vector Bd.
  • Aircraft magnetic detector or service detector 18 (Fig. 1) is now installed in the aircraft and if desired test detector 10 may be mounted immediately adjacent thereto by means of suction cups or other supportive devices. Upon installation, service detector 18 is physically aligned along the magnetic field prevailing inside the aircraft.
  • service detector 18 and, if present, test detector 10 are again subjected to relative rotation of its ambient magnetic field. While this relative rotation could be performed by physically rotating the detector, for convenience the coils contained in detectors 10 and 18 are biased by currents from networks 42 and 44 injected through switches 14 to simulate rotation.
  • the foregoing rotation allows microcomputer 34 to store new patterns of data.
  • Microcomputer 34 compares the patterns produced in the presence and absence of the aircraft for service detector 18 and, if present, test detector 10. Changes in the pattern of data are analyzed by a Fourier transformation subroutine in microcomputer 34. Accordingly, this differential data is resolved into spatial harmonics against the angular variable, azimuthal rotation of the detector.
  • microcomputer 34 iteratively alters the currents injected into service detector 18 by means of networks 42 and 44 through switches 14. This iterative alteration tends to approach the currents nominally required to produce an offsetting magnetic vector tending to cancel magnetic vector Bd (Fig. 2).
  • these offsetting currents are initially set at one-half of the nominal value and then adjusted as follows: Service detector 18 is electrically rotated as previously described and its response is compared to that previously occurring in the open field. The response of service detector 18 will tend to converge on the pattern of data produced in the open field due to the biasing currents.
  • biasing current (iterative) incrementation and the electrical rotation test are both repeated until convergence is obtained.
  • the biasing currents producing this convergence are now subjected to a conventional trigonometric analysis to determine the angular perturbation, angle p in FIGURE 2, represented thereby.

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Magnetic Variables (AREA)
EP81401420A 1980-09-29 1981-09-11 Dispositif pour calibrer un détecteur magnétique d'azimut dans un avion et méthode utilisant un détecteur de test Expired EP0052022B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US06/191,988 US4338810A (en) 1980-09-29 1980-09-29 Calibrator for a magnetic azimuth detector
US191988 1988-05-09

Publications (2)

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EP0052022A1 true EP0052022A1 (fr) 1982-05-19
EP0052022B1 EP0052022B1 (fr) 1985-11-21

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EP81401420A Expired EP0052022B1 (fr) 1980-09-29 1981-09-11 Dispositif pour calibrer un détecteur magnétique d'azimut dans un avion et méthode utilisant un détecteur de test

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US (1) US4338810A (fr)
EP (1) EP0052022B1 (fr)
JP (1) JPS5786713A (fr)
DE (1) DE3173005D1 (fr)
IL (1) IL63837A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112540202A (zh) * 2020-12-07 2021-03-23 杭州泰鼎检测技术有限公司 一种简易可调滤波器测试装置及方法

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5065521A (en) * 1990-08-01 1991-11-19 Honeywell Inc. Magnetic field measurement and compass calibration in areas of magnetic disturbance
US5557273A (en) * 1993-02-25 1996-09-17 Honeywell Inc. Magnetic azimuth detector to digital (MAD) converter
JP3872259B2 (ja) * 2000-07-26 2007-01-24 セイコーインスツル株式会社 磁気センサーの駆動電流調整方法及び電子方位計
US7259550B2 (en) * 2002-07-01 2007-08-21 European Organisation For Nuclear Research - Cern Device for calibration of magnetic sensors in three dimensions
US20080200807A1 (en) * 2007-02-20 2008-08-21 Accutome Ultrasound, Inc. Attitude-sensing ultrasound probe
US8108171B2 (en) * 2009-09-14 2012-01-31 Honeywell International, Inc. Systems and methods for calibration of gyroscopes and a magnetic compass
CN110127081A (zh) * 2019-04-23 2019-08-16 中航通飞华南飞机工业有限公司 一种便携式可变快速安装托架

Citations (7)

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US3683668A (en) * 1971-01-26 1972-08-15 Sperry Rand Corp Compass calibrator
US3942257A (en) * 1974-12-02 1976-03-09 Sperry Rand Corporation Index error correction for flux valve heading repeater system
US3991361A (en) * 1975-03-27 1976-11-09 Westinghouse Electric Corporation Semi-automatic compass calibrator apparatus for a vehicle mounted flux gate compass system to cancel out effect of local magnetic disturbances
US4031630A (en) * 1976-06-17 1977-06-28 The Laitram Corporation Calibration apparatus for automatic magnetic compass correction
US4109199A (en) * 1977-10-17 1978-08-22 The United States Of America As Represented By The Secretary Of The Navy Three axis magnetometer calibration checking method and apparatus
US4143467A (en) * 1978-05-01 1979-03-13 Sperry Rand Corporation Semi-automatic self-contained magnetic azimuth detector calibration apparatus and method
US4200933A (en) * 1976-07-30 1980-04-29 Systron-Donner Corporation Method of automatically calibrating a microprocessor controlled digital multimeter

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US2765649A (en) * 1952-12-02 1956-10-09 Warren C Youngclaus Device for determining deviation of magnetic compasses
US2887872A (en) * 1956-02-23 1959-05-26 Sperry Rand Corp Method of measuring and compensating for deviation errors for earth's field responsive instruments
US4091543A (en) * 1976-06-17 1978-05-30 The Laitram Corporation Automatic magnetic compass correction

Patent Citations (7)

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Publication number Priority date Publication date Assignee Title
US3683668A (en) * 1971-01-26 1972-08-15 Sperry Rand Corp Compass calibrator
US3942257A (en) * 1974-12-02 1976-03-09 Sperry Rand Corporation Index error correction for flux valve heading repeater system
US3991361A (en) * 1975-03-27 1976-11-09 Westinghouse Electric Corporation Semi-automatic compass calibrator apparatus for a vehicle mounted flux gate compass system to cancel out effect of local magnetic disturbances
US4031630A (en) * 1976-06-17 1977-06-28 The Laitram Corporation Calibration apparatus for automatic magnetic compass correction
US4200933A (en) * 1976-07-30 1980-04-29 Systron-Donner Corporation Method of automatically calibrating a microprocessor controlled digital multimeter
US4109199A (en) * 1977-10-17 1978-08-22 The United States Of America As Represented By The Secretary Of The Navy Three axis magnetometer calibration checking method and apparatus
US4143467A (en) * 1978-05-01 1979-03-13 Sperry Rand Corporation Semi-automatic self-contained magnetic azimuth detector calibration apparatus and method

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Title
1978 Wescon Technical Papers Vol. 22, 1978 T. CHELLSTORP "New Concepts in Calibrators", pages 1-12. * page 2, design concepts; figure 1 * *
IEEE Transactions on Geoscience Electronics, Vol. GE-16, No. 2, April 1978 R.L. McPHERRON et al. "A Procedure for Accurate Calibration of the Orientation of the Three Sensors in a Vector Magnetometer" pages 134-137. * pages 134, chapter II and 136, chapter III * *
Revue de Physique Appliguee, Vol. 5, February 1970 E.J. IUFER "Low Magnetic Field Technology for Space Exploration" pages 169-174. * page 172 "Magnetic Test Facilities" * *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112540202A (zh) * 2020-12-07 2021-03-23 杭州泰鼎检测技术有限公司 一种简易可调滤波器测试装置及方法

Also Published As

Publication number Publication date
EP0052022B1 (fr) 1985-11-21
US4338810A (en) 1982-07-13
JPS5786713A (en) 1982-05-29
DE3173005D1 (en) 1986-01-02
IL63837A (en) 1985-08-30

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